Coupling or connecting links are employed in a wide range of end-uses such as mooring buoys, drilling rigs, anchor chains, joining sections of wire rope or strand. The links are normally employed near salt or brackish water that enhances the corrosion rate of the links and reduces the useful life of the links.
Anchorage hardware and moorings used in marine applications are periodically inspected and subjected to routine maintenance. Due to corrosion, however, the inspection and maintenance process often requires additional time and cost. Detachable anchor links allow disassembly of anchor chain and are a key component of anchorage hardware. A detachable link comprise a C-link, two coupling plates, and a tapered pin. Some designs utilize a hairpin to lock in the tapered pin. Disassembly for routine maintenance becomes difficult when corrosion develops at the joint interfaces between the C-link and the coupling plates or in the joint interfaces between the coupling plates and the tapered pin. Typically, links are maintained by manually removing the lead sealant, disassembling the link, sand blasting the components of the link, applying a corrosion resistant material such as animal tallow containing powdered lead, reassembling the link and inserting the pin. Under normal use, the pin corrodes thereby inhibiting, if not preventing, removal of the pin and disassembly of the coupling links. In such cases, the link body must be cut, e.g., an acetylene torch, thereby destroying the link and delaying maintenance and usage of the entire article.
Detachable anchor links have previously been protected from corrosion by painting the exterior with an epoxy polyamide primer and a silicone alkyd enamel topcoat. Color coded striping paint is often applied as an outermost coating layer. The internal cavities of the detachable link are conventionally filled with a white lead filled beef tallow grease or more recently, greases that are not filled with elemental heavy metals. The toxic exposure to personnel and the undesirable environmental and regulatory aspects of utilizing the white lead have been mitigated by utilizing greases that do not contain the heavy elemental metals. However, many of the greases also contain base oils, inhibitors, or other additives that have significant aquatic toxicity. In addition, many greases do not offer sufficient water washout resistance for extended marine use. These issues have prompted the search for environmentally preferred lubricants and gels capable of withstanding the rigorous exposure of the marine environment.
Several coupling links and methods for maintaining chain are described in U.S. Pat. Nos. 4,179,878; 4,870,739; 5,351,359; and Design U.S. Pat. No. DES 287,102. The disclosure of these patents is hereby incorporated by reference.